The present invention relates to systems for subsurface fluid drainage and storage, and more particularly to apparatus for promoting, directing, and storing rain and irrigation water drainage on and below the land's surface, such as beneath sporting events fields.
There is little dispute among sporting facilities managers and landscapers that adequate drainage is a key to maintaining quality grass or turf on sporting events fields such as football and soccer fields, baseball diamonds, golf courses, and the like. In any landscape incorporating cultivated turf and subject to significant usage and traffic, it is highly desirable to anticipate and control water entering upon the surface from rainfall, irrigation, and runoff from adjacent areas such as bleachers or parking lots. In this disclosure and in the claims, the term "surface," unless specifically indicated otherwise, refers to the surface of the ground in an area where efficient drainage is desired, including sports fields whose surfaces are covered with cultivated turf grasses, but also including other landscapes with or without turf.
When sporting facilities and the like must be used in the presence of excess water (beyond that needed for turf or other desirable plant growth) at the surface and the root zone, physical destruction of the soil structure and root system can be so extensive and profound that facilities use must be suspended for several weeks while repair and/or regrowth occurs. Many facilities, however, are economically and/or practicably prevented from discontinuing use during extensive rest and repair periods due to intensive and inflexible sports competition and other use schedules. In many instances, sporting play must continue on surfaces of decreasing quality until after the end of the playing season. It is extremely desirable, therefore, to promote adequate drainage from sports and performance fields, certain portions of golf courses and public parks, and the like, in order to prevent the waterlogging that leads to physical breakdown and destruction of turf and other landscaped surfaces.
Furthermore, quality water is an increasingly valuable resource, particularly in large cities and in arid climates. Substantial quantities of rainwater fall and, especially in dry climates, tremendous volumes of irrigation water are applied to sports fields, golf courses, and other surfaces. Most of the water percolates into the subsurface and/or is lost as uncontrolled runoff, frequently carrying with it undesirable quantities of artificial fertilizers and pesticides. It is desirable, therefore, not only to promote thorough drainage from vulnerable surfaces, but to control and store the drained liquid for re-use, such as re-application to the landscaped surface.
Considerable previous effort has been expended in the field of subsurface drainage systems for sports fields and the like. U.S. Pat. No. 3,908,385 to Daniel, et al., teaches a system for removing quantities of water from a playing surface using perforated pipe networks and vacuum pumping. According to the disclosure, the vacuum pumps used to draw away water are actuated by electronic moisture sensors. The use of vacuum pumps imposes certain substantial cost and reliability impediments to widespread popular use of the system.
U.S. Pat. No. 4,023,506 to Robey teaches a system for reinforcing turf surfaces with netting components, and discloses subsurface drainage control by means of slitted pipe drains placed in trenches dug into a subsoil base and covered with a waterproof layer.
U.S. Pat. No. 4,044,179 to Haas, Jr., discloses an artificial pile fabric surface layer overlying layers of sifted sand for use on playing fields and the like. The high pile height of the surface fabric, and the granular nature of the sand layers are purported to conduct away excess water and reduce water accumulation after rainstorms.
U.S. Pat. No. 4,268,993 to Cunningham discloses a complex system for providing subsurface irrigation as well as drainage. An impermeable membrane overlaid with layers of sorted sand and gravel are described as directing liquid drainage to pipe drains.
U.S. Pat. No. 4,576,511 to Vidal, Jr. teaches an apparatus and method for creating and controlling an artificial water table, and incorporates a watertight membrane covered with a ballast layer of crushed rock, covered with a permeable layer which in turn is covered with a fine layer and a finish layer of increasingly finely divided rock or other material. As disclosed, drainage occurs by water gravity flow through the ballast layer of rock and along the watertight membrane to a central location for pumped removal.
U.S. Pat. No. 4,832,526 to Funkhouser, Jr. shows an underground watering system employing a series of slitted pipes to introduce irrigation water into the subsurface.
U.S. Pat. No. 4,881,846 to Burkstaller teaches subsurface drainage using perforated pipes surrounded by stone aggregate and placed above an impermeable layer.
U.S. Pat. No. 4,913,596 to Lambert, III discloses a simple subsurface drainage system fairly representative of the general concepts found in the known art and incorporating a subgrade formed with a series of ditches having drain tile therein exteriorly covered with pea gravel, a layer of pea gravel over the subgrade including the ditches having drain tile covered with pea gravel, a layer of crushed stone over the layer of pea gravel, a layer of sand over the layer of crushed stone, and a soil mixture on top of the layer of sand.
U.S. Pat. No. 5,064,308 to Almond, et al., likewise teaches a system for subsurface drainage incorporating a network of perforated pipes covered with successive layers of pea gravel and sand.
U.S. Pat. No. 5,219,243 to McCoy utilizes a vacuum pump to pull subsurface drainage water into perforated pipes buried in gravel.
Most of the systems known in the art are variations on a fundamental scheme of providing lateral drainage through one or more layers of sorted gravel or crushed rock. In the typical known system, a layer of gravel underlies the smaller-particle root zone. Water passing through the root zone reaches the gravel layer, and then presumably flows laterally through the gravel layer to a perforated pipe or French drain for discharge into a nearby surface watercourse or into a storm sewer system. Known systems however, are vulnerable over time as the gravel settles into an ever more densely packed layer. As find sands filter down and fill voids in the gravel, the gravel layer's fluid transmissivity is adversely affected. Additionally, gravel's tendency to settle reduces the desirability of placing pipes within a gravel layer, as severe settling and compaction may lead to pipe rupture.